Methods systems and apparatus for monitoring yield while harvesting grain

ABSTRACT

Systems, methods, and apparatus for monitoring yield while harvesting. In one embodiment, a mass flow rate sensor measures the mass flow rate of the harvested grain. Load sensors measure the weight of the harvested grain. The measured mass flow rate is correlated with the weight of the harvested grain. Processing circuitry calculates error in the measured mass flow rate using the measured weight. The calculated error is used to correct inaccuracy in the measured mass flow rate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 15/613,816,filed Jun. 5, 2017; which is a continuation of U.S. patent applicationSer. No. 14/868,366, filed Sep. 28, 2015, now U.S. Pat. No. 9,668,411;which is a continuation of U.S. patent application Ser. No. 13/996,700,filed Aug. 9, 2013, now U.S. Pat. No. 9,144,195; which is the NationalStage of International Application PCT/US2011/066826, filed Dec. 22,2011; which claims the benefit of U.S. Provisional Application61/426,376, filed Dec. 22, 2010. The entire disclosure of each of theseapplications is incorporated herein by reference.

BACKGROUND

FIG. 1A illustrates a conventional harvester or combine 10. As theoperator in cab 12 drives the combine 10 through the field, the cropbeing harvested is drawn through the header 15 which gathers the plantmaterial and feeds it into the feederhouse 16. The feederhouse 16carries the plant material into the combine where the grain is separatedfrom the other plant material. The separated grain is then carriedupward by the grain elevator 120 (FIG. 1B) to the fountain auger 150which carries the grain into the grain tank 20. The other plant materialis discharged out the back of the combine.

When the grain tank 20 becomes full, a transport vehicle such as graincart, wagon, or truck is driven up next to the combine or the combinedrives to the awaiting transport vehicle. The unloading auger 30 isswung outwardly until the end is positioned over the awaiting transportvehicle. A cross-auger 35 positioned in the bottom of the grain tank 20feeds the grain to the extended unloading auger 30 which in turndeposits the grain into the awaiting transport vehicle below.

Live or real-time yield monitoring during crop harvesting is known inthe art. One type of commercially available yield monitor uses a massflow sensor such as mass flow sensor 130 illustrated in FIG. 1B and asdisclosed in U.S. Pat. No. 5,343,761, “Method and Apparatus forMeasuring Grain Mass Flow Rate in Harvesters,” granted Sep. 6, 1994,which is hereby incorporated herein in its entirety by reference.Referring to FIG. 1B, as the grain 110 is discharged from the elevator120 it strikes an impact plate 140. Sensors associated with the massflow sensor 130 produce a voltage related to the force imposed on theimpact plate 140. The volumetric flow of grain can then be calculatedbased on the voltage such that the mass flow sensor 130 determines agrain flow rate associated with grain within the combine 10. Suchsystems also employ various methods of recording the speed of thecombine in operation. Using the speed and the width of the pass beingharvested (usually the width of the header), it is possible to obtain ayield rate in bushels per acre by dividing the mass of grain harvestedover a particular time period by the area harvested. In addition toreporting the current yield rate, such systems often incorporate GPS orother positioning systems in order to associate each reported yield ratewith a discrete location in the field. Thus a yield map may be generatedfor reference in subsequent seasons.

Most commercially available systems also utilize a sensor to determinethe moisture of the grain as it is being harvested. Sensing the grainmoisture permits the operator to determine the likely time or expenserequired to dry the harvested crop and it also allows the yield monitorto report more useful yield data by correcting for water content.Because grain is dried before long-term storage and sale (e.g., to anindustry-standard 15.5% moisture), the as-harvested moisture level canbe used to calculate the weight of saleable grain per acre.

While harvesting, various factors affect the reliability of the massflow sensor. Changes in crop yield, grain type, seed variety andgenetics, grain moisture, and ambient temperature are known to changethe flow characteristics of the grain and thus change the signalproduced by the sensor for the same mass flow rate. Due to thesechanging conditions during operation, it is well known that mass flowsensors may be inaccurate without proper calibration.

For this reason, manuals provided with commercially available yieldmonitors generally instruct the operator to occasionally carry out acalibration routine. Most commonly, when a load of grain is unloadedinto a weigh wagon or scale, the operator enters the measured weight ofgrain, and the yield monitor system applies a correction factor to itssignal by comparing the measured weight with its calculated accumulationof mass.

One of several disadvantages of this load-by-load calibration method isthat it is time-consuming and is often simply not performed on a regularbasis by the operator. Recognizing that many producers do not performregular calibrations and in an attempt to automate the calibrationprocess, some grain carts have been adapted to wirelessly transmit theload weight to the yield monitor system, as disclosed in U.S. Pat. No.7,073,314, “Automatic Mass-Flow Sensor Calibration for a Yield Monitor,”granted Jul. 11, 2006. However, where multiple grain carts are used,this method requires instrumentation of additional machines in order toobtain a load-by-load calibration, and no calibration is likely feasiblewhen the operator offloads grain directly into a grain truck.Additionally, load-by-load calibration may not be possible when, forexample, the grain tank can only be partially unloaded. Moreover, thismethod does not eliminate the inherent defects of load-by-loadcalibration discussed below.

Even if the operator or yield monitor system regularly performed acalibration routine, many of the conditions that affect the mass flowsensor change numerous times throughout accumulation of each load suchthat the calibration routine is unable to correct for such changes. Putanother way, the various changes in conditions that require mass flowsensor correction will rarely coincide with a load-by-load calibrationschedule. For example, a load of high-moisture grain may be harvestedand used to recalibrate the mass flow sensor just before entering adrier area of the field, causing the mass flow sensors to be moreinaccurate than if no calibration had been performed.

As such, there is a need for a system and method of accuratelycalibrating the mass flow rate sensor of a yield monitor whileharvesting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a conventional combine harvester.

FIG. 1B illustrates a conventional mass flow sensor.

FIG. 1C illustrates another embodiment of a mass flow sensor.

FIG. 1D illustrates yet another embodiment of a mass flow sensor.

FIG. 2A illustrates an embodiment of a process for calibrating a massflow sensor.

FIG. 2B illustrates another embodiment of a process for calibrating amass flow sensor.

FIG. 2C illustrates a calibration characteristic for a mass flow sensor.

FIG. 2D illustrates vehicle weight and mass flow sensor data.

FIG. 3 illustrates an embodiment of a system for calibrating a mass flowsensor.

FIG. 4A is a top plan view of an embodiment of a vehicle weight system.

FIG. 4B is a schematic elevation view of the front axle of a harvesterillustrating the loading on the front axle and the vehicle weight systemof FIG. 4A.

FIG. 4C is a top plan view of another embodiment of a vehicle weightsystem.

FIG. 4D is a flow diagram illustrating a process for detecting phantompayloads.

FIG. 5A is a cross-sectional view of an embodiment of an extensometer.

FIG. 5B is a cross-sectional view of the sensor holder as viewed alonglines B-B of FIG. 5A.

FIG. 5C is a perspective view of the magnet holder of FIG. 5A.

FIG. 6 is a process flow diagram illustrating a method of calibrating avehicle weight system.

FIG. 7A illustrates one embodiment of a system for measuring grainweight or the change in weight of the grain tank as it is filled withgrain.

FIGS. 7B-7E illustrate different views of another embodiment formeasuring grain weight or the change in weight of the grain tank as itis filled with grain.

FIG. 8 is a side elevation view of an embodiment of a head pressuresensor.

FIG. 9 illustrates a process for identifying non-trusted vehicle weightdata.

DETAILED DESCRIPTION Calibration Methods

Referring now to the drawings wherein like reference numerals designatethe same or corresponding parts throughout the several views, FIG. 2A isflow diagram showing steps of a preferred process 200 for calibrating amass flow sensor 130 (FIG. 1B). On initiation of the start step 210, twomeasurement steps 215 and 220 begin. At step 215, a mass flow ratesignal is obtained from a mass flow sensor. At step 220, a vehicleweight signal related to the vehicle weight of the combine harvester isobtained from a vehicle weight measurement system. At step 235, a massflow correction factor is preferably obtained from the prior run andmultiplied by the measured mass of grain harvested in order to obtain acorrected mass flow rate. At step 237, the corrected mass flowmeasurement is preferably reported, time-stamped, and stored for furtherprocessing. At step 250, an error between the mass flow signal and thevehicle weight signal is determined and new mass flow correction factoris calculated. The new mass flow correction factor is preferably storedfor use at step 235; that is, the new mass flow correction factor isapplied to subsequent measured mass flow rates.

The determination of error and calculation of a new correction factor atstep 250 can be performed according to various methods. One method is tosimply divide the integral of the mass flow signal by the change intotal vehicle weight. However, a first problem with this method is thatthe vehicle weight does not change simultaneously with the mass flowsignal, i.e., grain striking the impact plate 140 (FIG. 1B) of the massflow sensor 130 already affected the total vehicle weight at the pointof harvest. This problem may be partially corrected by measuring thetime during which the mass-flow sensor signal continues to read anon-zero value after the combine stops harvesting, and thentime-shifting the mass flow signal to better match the vehicle weightsignal. Another problem with this method is that the vehicle weightmeasurement at any given time, or even the change in measured vehicleweight between any two discrete times, may not be reliable due tochanging vehicle slope and other changing conditions (as discussed withrespect to the various embodiments of the vehicle weight system below).

Moreover, empirical data have shown that mass flow sensors arerelatively accurate during operation except when the combine encountersoccasional changes in field or crop conditions. When field or cropconditions change, the slopes of the measured cumulative mass flow datawill become significantly different than the slope of the measuredvehicle weight data whereby the data sets will begin to track away fromone another. An occasional slope correction to the mass flow sensor datawill “fit” the data sets closely, but the data sets must be monitored ona nearly continuous basis in order to apply the correction at theappropriate times.

In light of the problems and empirical results discussed above, anotherprocess for correcting weight at step 250 is shown by the flow diagramof FIG. 2B. In the FIG. 2B process, the necessity of a correction factoris determined based on the relative slope of the vehicle weight data andthe cumulative mass flow data. At step 252, a mass flow rate ispreferably obtained from a lookup table (described in further detailwith respect to FIG. 2C) in light of the signal from the mass flowsensor 130. At step 254 the mass flow rate as well as a cumulative sumof the mass flow rate is recorded and preferably time-stamped. At step256 the vehicle weight is recorded and preferably time-stamped. At step258, the processes of steps 252, 254 and 256 are repeated, preferablyuntil a measuring period T (e.g., 10 seconds) is reached. At steps 260and 262, the slope (i.e., rate of change) of the mass flow over time iscompared to the slope (i.e., rate of change) of the vehicle weight overtime. If the signs indicating direction of the slopes are different orthe absolute value of the slopes differ by more than a thresholdpercentage (e.g., 1 percent), then a new correction factor is calculatedat step 264. Otherwise the prior correction factor (if any) ispreferably retained at step 266. It should be appreciated that retainingthe prior correction factor may not comprise a positive algorithmicstep.

It should be appreciated that in addition to comparing rates of change,the flow-based weight change estimate may be compared over the recordingperiod T to a weight-based weight change estimate (preferably derivedfrom the difference in the weight signal at the beginning and end of therecording period) such that an appropriate correction factor may bedetermined.

The lookup table preferably consulted at step 252 preferably comprises aset of calibration curves 280 as illustrated in FIG. 2C. The response ofsome commercially available impact type mass flow sensors is non-linearwith the mass flow rate as is well known in the art. The shape of thisnon-linear relationship may vary with factors such as grain type,vehicle incline, and moisture content. Thus a set of calibration curves280 corresponding to each range of such factors may be empiricallydeveloped and consulted to determine the mass flow rate of the sensor atstep 252.

The calculation of a new correction factor at step 264 is carried out tobest fit the cumulative mass flow rate data to the vehicle weight dataover measuring period T or multiple measuring periods T. The correctionfactor may comprise a single linear multiplier. FIG. 2D is anillustrative data set 270. Data set 270 includes a vehicle weight data272 (represented by a scatter plot) and cumulative mass flow rate data271 (represented by a line plot). Over measuring period T (in FIG. 2D,60 seconds), the slope of cumulative mass flow rate data 271 differssignificantly from the slope of vehicle weight data 272. Thus acorrected slope (illustrated by line 271′) is preferably used. Toachieve this, a correction factor (k) is calculated as the ratio betweenthe slope of line 271′ and slope of a line that best fits mass flow ratedata 271.

It should be appreciated that more complex correction method may be usedto fit the data sets rather than multiplying by a constant. For example,an alternative method may determine the requisite coefficients to inputthe mass flow sensor data into a first-order, second-order, third-order,or fourth-order polynomial that best fits the vehicle weight data overthe measuring period T. It should also be appreciated that in someapplications, signal processing methods known in the art (such asanti-aliasing or low-pass filters) may be applied to either or both ofthe vehicle weight and mass flow rate signals in order to avoidrecording erroneous data.

Calibration Systems

FIG. 3 is a schematic illustration of a calibration system 300preferably used to carry out the process 200. The calibration system 300preferably includes a vehicle weight system 400, a yield monitor board310, a monitor system 320, a moisture sensor 330, an auger weight sensor335, a speed sensor 340, one or more gyroscopes 345, one or moreaccelerometers 350 (preferably three-axis accelerometers), a GPS system355, a mass flow sensor 130, a head pressure sensor 380 and a mass flowsensor 130.

The monitor system 320 preferably includes a display unit 324 andprocessing circuitry including a central processing unit (CPU) 322. Thedisplay unit 324 is preferably a graphical user interface configured toallow the operator to enter commands. The monitor system 320 ispreferably mounted in the cab 12 (FIG. 1A) of the combine 10 such that auser can view the display unit 324. In some embodiments, the monitorsystem 320 may also be configured to display planting information suchas that disclosed in U.S. Pat. No. 8,386,137, “Planter Monitor Systemand Method,” granted Feb. 26, 2013, incorporated herein in its entiretyby reference. In such embodiments, the monitor system 320 is preferablyconfigured to display maps overlaying planting information with yielddata and to compare planting information to yield data.

The yield monitor board 310 is preferably mounted to the combine 10. Thegyroscope 345 and accelerometer 350 are preferably in electricalcommunication with the yield monitor board 310 and mounted thereto. Thespeed sensor 340, the moisture sensor 330, mass flow sensor 130, headpressure sensor 380 and vehicle weight system 400 are all preferably inelectrical communication with the yield monitor board 310 which is, inturn, in electrical communication with the monitor system 320. The GPSsystem 355 is also preferably in electrical communication with themonitor system 320.

The speed sensor 340 is preferably configured to measure the speed of anaxle of the combine as is known in the art. Upon each rotation orpartial rotation of the axle, the speed sensor 340 preferably sends anencoder pulse to the yield monitor board 310. The monitor system 320preferably determines the speed of the axle from the time between eachencoder pulse.

Vehicle Weight Measurement Systems

FIG. 4A illustrates one embodiment of the vehicle weight system 400. Thevehicle weight system 400 generally includes a set of extensometers 500(described in detail later) attached to the combine 10. As illustrated,the combine 10 includes front tires 410, front axle 422, rear tires 415,and rear axle 427. One embodiment of the vehicle weight system 400includes a pair of front extensometers 500 f 1 and 500 f 2 mounted tothe front axle 422, and a pair rear extensometers 500 r 1 and 500 r 2mounted to the rear axle 427. Each extensometer 500 has a rightmost endand a leftmost end and is preferably mounted to the respective axle attwo locations near the rightmost end and near the leftmost end. Eachextensometer 500 is preferably mounted using brackets 460 (FIG. 4B) orother suitable apparatus fixed securely to the respective axle. Eachextensometer 500 is preferably in substantial alignment with therespective axle to which it is mounted. Each extensometer 500 ispreferably in electrical communication with the yield monitor board 310.

In operation of the vehicle weight system 400, the weight of combine 10is carried by the axles, 422, 427 which transfer the load to the frontand rear tires 410, 415, respectively. Thus, bending stresses areimposed on the front axle 422 and the rear axle 427. FIG. 4B is aschematic illustration of the loads acting on the front axle 422. Theportion of the weight of the combine 10 carried by the front axle 422 isidentified as Fw. The weight Fw is applied at two points where thecombine frame is attached to the axles, resulting in a force Fw/2 ateach point of attachment. The load Fw is transferred to the soil by thefront tires 410 resulting in a reaction force designated by forces Frand Fl at each front tire 410. Although not shown, corresponding loadsand reaction forces resulting in bending stresses are experienced by therear axle 427. It should be appreciated that as the load on the axles422, 427 increases due to more grain being added to the grain hopper asthe crop is being harvested, the bending stresses on the axles willincrease. These increased bending stresses will result in the inwarddisplacement of the brackets 460 toward one another as the axle bends asshown exaggerated by hidden lines in FIG. 4B. As the brackets aredisplaced inwardly, the extensometers 500 generate a correspondingincrease in voltage which is communicated to the yield monitor board310. The sum of the voltages from the extensometers 500 is proportionalto the weight of the combine 10 and the magnitude of the force Fwimposed on each axle.

In some embodiments, the front extensometers 500 f 1 and 500 f 2 may beomitted such that only the rear axle 427 is instrumented withextensometers 500 r 1 and 500 r 2. It should be appreciated that in suchembodiments the accuracy of the vehicle weighing system will becompromised; nevertheless, after a longer period of operation such anembodiment would still provide a useful indication of how far the massflow sensor 130 has “drifted” according to the methods described withrespect to FIGS. 2A and 2B.

Vehicle Weight Measurement Apparatus

FIG. 5A illustrates a cross-section of an embodiment of an extensometer500. The extensometer 500 preferably includes a conduit 510, a sensor530, a sensor holder 535, a magnet 520, and a magnet holder 525.

The conduit 510 is mounted at a first end to a first bracket 460. Thesensor holder 535 is fixed (e.g., press fit) within the conduit 510. Atube 515 is preferably mounted within the sensor holder 535. As bestseen in FIG. 5B, the sensor 530 is housed within the tube 515,preferably by potting.

The magnet holder 525 is slidably housed within the conduit 510. Themagnet holder 525 is fixed to a rod 550. The rod 550 is fixed to asecond bracket 460 near a second end of conduit 510. The magnet 520 ispreferably mounted within the magnet holder 525, as best viewed in FIG.5C. The magnet 520 preferably includes an aperture 522. The magnetholder 525 includes a cavity 527. The tube 515 preferably extendsthrough the magnet aperture 522 and into the magnet holder cavity 527.The tube is preferably radially constrained by an o-ring 532 housedwithin magnet holder 525.

The sensor 530 may be any sensor configured to emit a signalproportional to a magnetic field experienced by the sensor. The sensor530 is preferably a Hall Effect sensor such as model number A1392available from Allegro MicroSystems, Inc. in Saitama, Japan. The sensor530 is in electrical communication with the yield monitor board 310.

In operation, as the brackets 460 move relative to one another asdescribed above and illustrated in FIG. 4B, the magnet holder 525 moveswithin the conduit 510 such that the magnet holder 525 and sensor holder535 move relative to one another. Thus the sensor 530 moves within theaperture 522 in the magnet 520. The magnet 520 develops a magnetic fieldwithin the aperture 522. The magnitude of the magnetic field variesalong the width of the magnet 520 (right-to-left as viewed in FIG. 5A).As the sensor 530 moves within the magnetic field, the sensor 530 sendsa signal to the yield monitor board 310, the voltage of which signal isproportional to the magnitude of the magnetic field at the location ofsensor 530. Thus the voltage produced by the sensor 530 is related tothe position of the sensor 530 within the magnet 520. Likewise, thevoltage produced by the sensor 530 is related to the relativedisplacement of the brackets 460.

It should be appreciated that other embodiments of the extensometer 500may include a magnet 520 having a different shape and differentlocations of the sensor 530 with respect to the magnet 520. However, theembodiment described with respect to FIGS. 5A-5C is preferable becausewithin the aperture 522, the magnitude of the magnetic field adjacent tothe magnet 520 varies substantially and with substantial linearitywithin the aperture along the width of the magnet 520.

It is preferable to use two extensometers 500 mounted to each axle dueto complex loading scenarios experienced by the axles during operation.For example, if one of the axles were placed in forward or rearwardbending in the direction of travel of the combine 10 (i.e., transverseto the vertical forces Fw illustrated in FIG. 4B), the brackets 460would experience relative displacement unrelated to a change in weightof the combine 10. However, with two extensometers 500, such bendingmoves one pair of brackets 460 farther apart while moving the other pairof brackets 460 closer together, such that the sum of the voltages sentby the extensometers 500 remains substantially unaffected. A similarreduction in error is observed if either axle is placed in torsion. Itshould also be appreciated that the extensometers 500 may be mounted tothe bottom of the axles 422, 427 such that the brackets 460 move fartherapart as the weight of the combine 10 increases.

Processing Mass Flow Data

The calibration system 300 also preferably processes the corrected massflow data into yield data. While the calibration method described withrespect to FIGS. 2A and 3 is carried out while harvesting, the correctedmass flow data are stored by the monitor system 320. The monitor system320 preferably integrates mass flow data over each discrete monitoringperiod (T) (for example, five seconds) during operation to obtain themass (m) of accumulated grain during that monitoring period T. The userpreferably enters the width of the header (i.e., header width (W_(h)))into the monitor system 320 prior to operation. The monitor system 320determines a distance traveled (D) by integrating the speed (measured,e.g., by the speed sensor 340) over the monitoring period T. The yield(Y) can then be calculated using the following equation:

$Y = \frac{m}{{DW}_{h}}$

The yield data may be corrected for moisture using the signal from themoisture sensor 330 and reported in dry bushels per acre as is known inthe art. The locations in the field associated with each monitoringperiod T are established using the GPS system 355 and recorded by themonitor system 320. The GPS and yield data may then be used to produce ayield map illustrating the spatial variation in yield.

Vehicle Weight System Calibration Methods

Under some methods of calibrating of the vehicle weight system 400,appropriate multipliers are preferably determined to apply to the signalsent by each extensometer 500 such that the sum of the signalsmultiplied by their individual multipliers is substantially proportionalto the weight of the combine 10. FIG. 6 is a flow diagram showing aprocess 600 for calibrating a vehicle weight system. At step 610, themonitor system 320 records the signals V₁ through Vn sent by eachextensometer 500. At step 620, the monitor system directs the operatorto perform a calibration maneuver such that the various tires carrydifferent fractions of the weight of the combine 10. For example, themonitor system may instruct the operator to drive the combine on asubstantially flat surface at a given speed.

Because the total weight of the combine 10 does not change substantiallythroughout the calibration maneuver, the relationship between thesignals Vn may be modeled by a relationship such as:

$W = {\sum\limits_{n = 1}^{N}{C_{n}{V_{n}(t)}}}$

Where:

-   -   W—is a constant because the weight of the combine is constant        (note: W may not represent the actual weight of the combine 10)    -   V_(n)—represents the signal sent by the nth extensometer 500    -   C_(n)—is a coefficient representing a calibration factor or        multiplier associated with the nth extensometer 500.    -   t—is time in seconds.

Thus, at step 630 the monitor system 320 preferably determines the setof coefficients C_(n) that result in a constant value W throughout thecalibration maneuver. It should be appreciated that in some cases aconstant value W may not be obtained in practice, in which case themonitor system preferably determines the set of coefficients C_(n) thatresult in the smallest variation (e.g., standard deviation) of Wthroughout the calibration maneuver.

At step 640, a known weight is added or removed from the system. Forexample, the header 15 may be removed from the combine 10 such that thetotal weight of the combine decreases by the known weight of the header.At step 650, new coefficients C_(n) are calculated so that the change inW is equal to the known change in weight of the combine. For example,the coefficients C_(n) may be multiplied by a single constant equal tothe decrease in W divided by the known change in weight (e.g., theweight of the header 15). At step 660, the monitor system 320 preferablystores the new coefficients C_(n) for application to subsequent weightmeasurements.

In an optional setup phase prior to the calibration described in processflow diagram 600, the monitor system 320 preferably instructs theoperator to carry out a routine similar to the calibration routine 620such that the fraction of weight carried by the various tires changes.As each subroutine is carried out, the monitor system 320 evaluates thechange in the signals V_(n) and determines whether the changes insignals correspond to the expected change in the fraction of weightcarried by each tire. For example, if the monitor system instructs theoperator to accelerate the vehicle, an increase in the signals from therearwardly disposed front and rear extensometers 500 f 2 and 500 r 2should be observed. If no such change is observed, the monitor system320 preferably instructs the operator to ensure that the rearwardlydisposed extensometers 500 f 2 and 500 r 2 are properly installed.

In an optional system evaluation phase, the monitor system 320determines new coefficients C_(n) (as performed at step 630 in processflow 600) while the combine 10 is moving but not harvesting. As anexample, the monitor system 320 may initiate step 630 of process 600when the GPS system 355 indicates that the combine 10 is moving fasterthan 10 miles per hour or any predetermined speed above which thecombine 10 is likely in a transport mode and not harvesting. It shouldbe appreciated that calculating new coefficients C_(n) while intransport is preferable because the weight of the combine 10 is shiftingbetween the load-bearing members but the combine is not accumulatinggrain.

Non-Trusted Data

In operation of the vehicle weight system 400, certain environmental andoperating parameters occasionally cause inaccuracy of the vehicle weightdata. Such data is preferably identified by the monitor system and ispreferably not used to calibrate the mass flow rate signal provided bythe mass flow sensor 130.

Thus, a preferred process 900 for filtering non-trusted vehicle weightdata is shown in the flow diagram of FIG. 9. At step 200 the monitorsystem 320 preferably calibrates the mass flow rate signal using thevehicle weight according to the process 200 described with respect toFIG. 2A. At step 910 the monitor system 320 preferably monitors a dataquality criterion. The data quality criterion preferably comprises asignal corresponding to the accuracy of data generated by the vehicleweight system 400. At step 920, the monitor system 302 preferablycompares the data quality to a predetermined threshold. The thresholdmay comprise a predetermined percentage or number of standard deviationsfrom of the average data quality criterion or simply a predeterminedvalue. The threshold preferably lies between a non-desired data qualityrange and a desired data quality range.

If the data quality criterion exceeds the threshold, then at step 930the monitor system preferably calibrates the mass flow rate signal withvehicle weight data. In carrying out the step 930, the monitor system320 preferably continues recording data from the vehicle weight system400, but stops using the vehicle weight system. In embodiments in whichthe monitor system 320 calibrates mass flow sensor using a correctionfactor (e.g., as described with respect to FIG. 2B), the monitor systemmay continue using the last correction factor calculated before the dataquality criterion exceeded the trusted data threshold.

At step 940 the monitor system preferably determines whether the dataquality criterion is below the trusted data threshold (i.e., whethervehicle weight data can again be trusted). If so, at step 950, themonitor system 320 preferably resumes calibration of mass flow rate withvehicle weight data.

Non-Trusted Data—Unloading Operations

During operation of the calibration system 300, the operator willoccasionally activate the unloading auger 30 of the combine 10 in orderto remove accumulated grain 110 from the grain tank 20 of the combine.Often this operation is carried out while harvesting, with a tractorpulling a grain cart or auger wagon alongside the combine 10. Duringsuch operations, the weight of the combine changes due to unloading andthus vehicle weight should not be used to calibrate the mass flow sensor130 as described herein. Thus an auger weight sensor 335 is preferablyincluded in the embodiment of the calibration system 300 as illustratedin FIG. 3.

The weight sensor 335 may comprise a strain gauge attached to anyload-bearing member of the combine 10 bearing the weight of theunloading auger 30 and configured to measure the deformation (e.g.,strain) of the load-bearing member, or any other sensor configured tosend a signal proportional to the weight of the unloading auger 30. In asetup phase, the monitor system 320 records a value of the signal fromthe auger weight sensor 335 when there is no grain in the unloadingauger 30. In operation, when the combine unloads grain through theunloading auger 30, the weight of the unloading auger increases and thesignal from the auger weight sensor 335 increases. When the signal fromthe auger weight sensor 335 reaches a threshold level in excess of thevalue recorded in the setup phase, the monitor system 320 entersnon-trusted data mode as described with respect to FIG. 9. It should beappreciated that when the unloading auger 30 is turning, the frequencycontent of the auger weight sensor signal will change because theunloading auger will undergo substantial vertical vibration. Thus in analternative method, the frequency spectrum of the auger weight sensorsignal is used to determine when the auger is turning. When the augerweight sensor signal includes a frequency component within apredetermined range having an amplitude within a predetermined range,the monitor system 320 preferably enters non-trusted data mode.

In addition, the signal from the auger weight sensor 335 may be used todetermine whether the grain tank 20 has been completely emptied. If theoperator unloads only a portion of the grain tank 20 and stops theunloading auger 30, then the frequency of auger weight sensor signalwill return below its threshold value (indicating that the unloadingauger is not rotating) but the value of the signal will remain above itsthreshold value because the unloading auger cannot empty until the graintank 20 is emptied. Thus when the auger weight sensor signal returnsbelow its threshold value, the monitor system 320 preferably determinesthat the grain tank 20 is empty and may perform any step that requiresan empty grain tank, such as comparing the sum of the extensometersignals to the sum measured during setup or visually indicating to theoperator that the grain tank is empty.

Non-Trusted Data—Vehicle Dynamics

The accelerometer 350 is preferably oriented and configured to send asignal to the yield monitor board 310 related to the acceleration ordeceleration of the combine 10 along the direction of travel. Becauseexcessive acceleration or deceleration can impose excess loads on thevehicle weighing apparatus, the monitor system 320 preferably enters thenon-trusted data mode when the accelerometer signal exceeds a predefinedthreshold value. Similarly, the gyroscope 345 is preferably oriented andconfigured to send signals to the yield monitor board 310, which signalsare related to the pitch and roll of the combine 10. Because excessivepitch or roll of the combine 10 causes the vehicle weighing apparatus toundergo loads which may not be directly related to the weight of thecombine, the monitor system 320 preferably enters the non-trusted datamode when either of the gyroscope signals exceeds predefined thresholdvalues.

Non-Trusted Data—Head-Ground Contact

It should be appreciated that when the header 15 contacts the ground,the ability of a vehicle weight system 400 to weigh the combine 10 iscompromised because a portion of the vehicle weight is carried by thehead. Thus the header pressure sensor 380 may be used in applications inwhich the header 15 occasionally or regularly contacts the ground. Theheader pressure sensor 380 may comprise any pressure sensor configuredto produce a signal corresponding to the pressure in one or morehydraulic actuators used to position the header 15. FIG. 8 illustrates aheader pressure sensor 380 in fluid communication with the work chamber810 of a hydraulic actuator 800. In the illustrated embodiment, theheader pressure sensor 380 is installed such that fluid from a pressuresupply line 820 flows through the header pressure sensor 380 beforeentering the work chamber 810. The header pressure sensor 380 maycomprise a pressure transducer such as those manufactured by GemsSensors & Controls in Plainville, Conn. The header pressure sensor 380sends a signal to the yield monitor board 310 corresponding to thepressure in the work chamber 810.

In operation, the monitor system 320 preferably compares the signal fromthe header pressure sensor 380 to a threshold value corresponding to thepressure required to hold up the header 15 just above the surface. Asthe pressure decreases below the threshold pressure, the difference inpressure corresponds to the weight of the header carried by the ground.During operation, the monitor system 320 preferably subtracts thisweight from the vehicle weight measured by the vehicle weight system400. In some applications, particularly where it is not expected thatthe header 15 will contact the ground frequently during operation, thesignal from the header pressure sensor 380 may be used simply todetermine whether the monitor system 310 should enter non-trusted datamode.

Non-Trusted Data—Phantom Payload

In some embodiments, the monitor system 320 also preferably entersnon-trusted data mode when the effective point of loading on tires 410shifts. FIG. 4C illustrates a combine 10 having dual front tires 410 asis common in commercially available combines. In operation, if theweight of the combine 10 shifts off of an inside dual tire and onto anoutside dual tire (as, for example, when the outside dual tireencounters a steep slope or obstruction) the effective point of loadingshifts away from the center of the front axle 422. Thus the bending ofthe front axle 422 increases such that the signal from extensometers 500f 1 and 500 f 2 increases, even though the weight of the combine has notchanged. This false signal is described herein as “phantom signal” andthe resulting calculated load is described herein as “phantom payload.”

To detect phantom payload, the embodiment of the vehicle weight system400 illustrated in FIG. 4C preferably includes dual extensometers 500 dl1 and 500 dl 2 between the left front tires 4101 and the extensometers500 f 1 and 500 f 2. In addition, the same embodiment preferablyincludes dual extensometers 500 dr 1 and 500 dr 2 between the rightfront tires 410 r and the extensometers 500 f 1 and 500 f 2. The dualextensometers 500 d are preferably mounted to the combine 10 using abracket or other suitable apparatus. The dual extensometers 500 d are inelectrical communication with the yield monitor board 310. It will beappreciated in light of the disclosure of this application that a singleextensometer 500 d may be mounted near each dual tire 410, but twoextensometers are preferably included (as illustrated in FIG. 4C) tocancel the effects of torsion and non-vertical bending. When the sum ofthe signals from either pair of dual extensometers 500 d exceeds athreshold value, the monitor system 320 preferably enters a non-trusteddata mode.

Using the vehicle weight system embodiments described herein withrespect to FIG. 4C, the monitor system 320 may detect phantom payloadwhen the ratio between the signals from either pair of additional dualextensometers 500 d and the front extensometers 500 f exceeds athreshold value. In one method, the monitor system 320 may simply enterthe non-trusted data mode when phantom payload is detected. However,according to another method as shown in the flowchart of FIG. 4D, themonitor system 320 may also calculate and subtract the detected phantompayload from the measured payload. In the process flowchart 480 of FIG.4D, at step 481, the monitor system preferably determines that thecombine 10 is harvesting according to a number of indicators, including:(a) whether the head is lowered using the head weight sensor 380; (b)whether vertical acceleration is noisy using the accelerometer 350; (c)whether the combine is turning using the gyroscope 345; or (d) whetherthe combine speed is within a predetermined range (e.g., two and sevenmiles per hour) using the GPS system 355 or speed sensor 340.

If the combine 10 is harvesting, then at step 482 the monitor system 320determines whether the roll of the combine is within an acceptablepredetermined range using the gyroscope 345. If the roll is acceptable,the combine preferably adjusts the front-axle and dual extensometersignals at step 483 to calculated “no pitch” signals by determining thepitch using the accelerometer 350, determining a pitch factor by whichthe front axle load is affected due to combine pitch, and dividing thesignals by the pitch factor. At step 484 the monitor system 320preferably determines predicted “no-pitch” dual extensometer signalsusing the mass flow sensor 360 to determine the change in grain weight.At step 485, the monitor system 320 preferably subtracts each predicted“no-pitch” dual extensometer signal from the corresponding calculated“no-pitch” dual extensometer signal to obtain the “phantom signal.” Atstep 486, the monitor system 320 preferably applies the multiplierscalculated for the dual extensometers 500 d (as described with respectto FIG. 6) to each “phantom signal” and sums the “phantom signals” toobtain the total “phantom payload.” At step 487, the monitor system 320preferably subtracts the “phantom payload” from the total “no-pitch”load on the front axle 422 to obtain the corrected “no-pitch” load onthe front axle. At step 488 the monitor system 320 preferably readjuststhe “no-pitch” load on the front axle 422 by multiplying it by the pitchfactor calculated at step 483. Thus the monitor system 320 is able toremove “phantom payload” from the measured vehicle weight.

Alternatives—Vehicle Weight Systems

It should be appreciated that the method of calibrating the mass flowsensor 130 described herein, as well as the system for performing themethod, could be carried out with any apparatus configured to measurethe weight (or change in weight) of the combine 10 or of the grain tank20 containing clean grain 110. FIG. 7A illustrates an alternativeembodiment of the vehicle weight system 400 in which the grain tank 20of the combine 10 is supported by load cells 720. Each load cell 720 isfitted with strain gauges or other devices configured to send a signalproportional to the compression of the load cell. In the illustratedembodiment, the grain tank 20 includes upper and lower ridges 750 u and750 l. The load cells are mounted between the ridges 750 and the combineframe. It should be appreciated that other embodiments of the vehicleweight system may include load cells 720 in other locations andorientations supporting the weight of the grain tank 20.

However, as best viewed in FIG. 1A, in most commercially availablecombines the grain elevator 120 and cross-auger 35 both compriseload-bearing and load-imposing members with respect to the grain tank20, such that it is difficult to determine the weight of the grainwithin the grain tank without modifying the structure of the combine 10.

Thus a modified combine 10 incorporating another embodiment of thevehicle weight system 400 is illustrated in FIGS. 7B-7E. In thisembodiment, the weight of the grain tank 20 is isolated from othermembers of the combine 10 and supported by load cells 720. The grainelevator 120 passes through the wall of the tank 20 without imposingsignificant loads on the tank, preferably via a seal 123 which may beconstructed of any material (e.g., rubber) suitable for sealing grain inthe tank while allowing the grain elevator 120 and the grain tank 20 tomove relative to one another. Additionally, the cross-auger 35 islocated below a transverse slot 38 in the grain tank 20 such that grainfalls from the tank into the cross-auger for conveyance to the unloadingauger 30. In such embodiments, a selectively closable gate or door (notshown) over the cross-auger 35 at the bottom of the grain tank 20 ispreferably incorporated to retain grain in the grain tank when grain isnot being unloaded. Substantially all the weight of the tank 20 thusrests on the grain tank support legs 36. Load cells 720 are interposedbetween grain tank support legs 36 and support members 37 of the combineframe.

It should be appreciated that in the embodiments described above withrespect to FIGS. 7B-7E, the support structure and weight measurementsystem could be modified significantly while still obtaining ameasurement related to the weight of the grain tank 20. In someembodiments, the support legs 36 could be joined directly (by welding orby joints) to the support members 37 and the support legs 36instrumented with strain gauges. In other embodiments, the support legs36 could be joined to the support members 37 by instrumented pins.

In the embodiments discussed above with respect to FIG. 7A or theembodiments discussed above with respect to FIGS. 7B-E, each load cell720 is in electrical communication with the yield monitor board 310. Itwill be appreciated that the sum of the signals from the load cells 720sent to the tank is proportional to the weight of the grain tank and itscontents. Calibration of the embodiment of the vehicle weight system 400may be accomplished by recording a first sum of the load cell signals S₁when the grain tank 20 is empty, adding a known weight w_(cal) to thegrain tank, and recording a second sum of the load cell signals S₂ withthe known weight in place. The ratio of w_(cal) to the differencebetween S₂ and S₁ constitutes a calibration characteristic k (in unitsof, for example, pounds per millivolt). Thus, as grain is added to thetank during operation, grain weight w_(g) may be represented in terms ofthe currently recorded sum of load cell signals S as follows:

W _(g) =k(S−S ₁)

In some embodiments, the response of the load cells may be non-linearsuch that the calibration characteristic k should be replaced with acharacteristic curve (e.g., curve 280 of FIG. 2C) relating a set ofknown weights to load cell signals. In other embodiments, it may bepreferable to carry out a calibration maneuver and obtain a set ofmultipliers corresponding to each load cell 720 as described withrespect to FIG. 6.

Alternatives—Mass Flow Sensors

It should also be appreciated that the mass flow sensor 130 need notcomprise the impact plate type illustrated in FIG. 1B but may compriseany sensor configured to send a signal corresponding to the mass flowrate of grain in the combine 10. For example, FIG. 1C illustrates agrain elevator 120 driven by a driveshaft 122. A torque sensor 124 iscoupled to the drive shaft 122. The torque sensor 124 is in electricalor wireless communication with the yield monitor board 310. The torquesensor 124 may be an inline rotary torque sensor such as those availablefrom FUTEK Advanced Sensor Technology, Inc in Irvine, Calif. The torquesensor 124 is preferably configured to produce a signal corresponding tothe torque on the drive shaft 122. The torque on the drive shaft 122increases with the weight of grain 110 being carried by the grainelevator 120. Thus the signal from torque sensor 124 may be used tomeasure the weight of grain 110 in the grain elevator 120 at a giventime. According to one method of using the embodiment of the mass flowsensor 130, the speed of the drive shaft 122 may be measured using aspeed sensor similar to speed sensor 340 or other suitable apparatus.Using the speed of the drive shaft 122 and known length of the grainelevator 120, the yield monitor board preferably determines when thegrain elevator has made a complete cycle and records the weight of thegrain 110 added to the combine in each cycle.

In another embodiment of the mass flow sensor 130 illustrated in FIG.1D, driveshaft 122 is driven by an electric or hydraulic motor 126. Thepower drawn by the motor 126 is measured as is known in the art andreported to the yield monitor board 310. Like the torque on thedriveshaft 122, the power drawn by the motor 126 is related to theweight of grain 110 in the grain elevator 120 and may be used by themonitor system 320 to measure a flow rate of grain 110 according to themethod described above.

In other embodiments, the mass flow sensor 130 may comprise an apparatusused to measure the weight of the clean grain 110 as it moves throughthe combine 10 as is disclosed in U.S. Pat. No. 5,779,541, “CombineYield Monitor,” granted Jul. 14, 1998, the disclosure of which is herebyincorporated by reference in its entirety.

Other types of mass flow sensors which may be calibrated by the methoddescribed herein include optical mass flow sensors as are known in theart.

The foregoing description is presented to enable one of ordinary skillin the art to make and use the systems, methods and apparatus describedherein and is provided in the context of a patent application and itsrequirements. Various modifications to the preferred embodiment of theapparatus, and the general principles and features of the system andmethods described herein will be readily apparent to those of skill inthe art. Thus, the invention is not to be limited to the embodiments ofthe apparatus, system and methods described above and illustrated in thedrawing figures, but is to be accorded the widest scope consistent withthe spirit and scope of this disclosure and the appended claims.

1. A method for monitoring yield while harvesting grain with aharvester, the method comprising: generating a flow rate signal relatedto a grain flow rate within the harvester with a mass flow rate sensor;generating a plurality of load signals related to compressive forces onload cells by grain in a grain tank of the harvester; and correlatingthe flow rate signal with the load signals to monitor yield whileharvesting grain.
 2. The method of claim 1, wherein correlating the flowrate signal and the load signals comprises: determining a rate of changeof the plurality of load signals; and comparing the rate of change ofthe plurality of load signals to the flow rate signal.
 3. The method ofclaim 1, wherein correlating the flow rate signal and the load signalscomprises: integrating the flow rate signal over a recording period toobtain a flow-based weight change estimate; determining a change in theload signals over the recording period to obtain a load-based weightchange estimate; and comparing the flow-based weight change estimate tothe load-based weight change estimate.
 4. The method of claim 1, furthercomprising: determining an error associated with the flow rate signal;and correcting the flow rate signal.
 5. The method of claim 1, furthercomprising estimating a mass of grain in the grain tank based on theplurality of load signals.
 6. The method of claim 5, wherein estimatinga mass of grain in the grain tank comprises calibrating the load cellswhile an amount of grain in the harvester remains substantiallyunchanged.
 7. The method of claim 1, further comprising: determining anerror associated with the flow rate signal based on the load signals;correcting the flow rate signal using the error to generate a correctedmass flow measurement; and displaying the corrected mass flowmeasurement.
 8. The method of claim 1, further comprising: generating adata quality criterion associated with the load signals; comparing thedata quality criterion to a desired range; determining an errorassociated with the flow rate signal using values of the load signalsrecorded while the data quality criterion was within the desired range;correcting the flow rate signal using the error to generate a correctedmass flow measurement; and displaying the corrected mass flowmeasurement.
 9. The method of claim 1, wherein generating a plurality ofload signals related to compressive forces on load cells by grain in agrain tank of the harvester comprises generating at least three loadsignals related to at least three compressive forces on at least threeload cells by the grain in the grain tank.
 10. A system for monitoringyield while harvesting grain with a harvester, comprising: a mass flowsensor configured to generate a flow rate signal corresponding to a flowrate of grain within the harvester; a grain tank comprising a pluralityof load cells, each load cell configured to generate a load signalproportional to a compressive force on the load cell by grain in thegrain tank; and processing circuitry in electrical communication withthe mass flow sensor and the plurality of load cells, the processingcircuitry configured to calculate an error in the flow rate signal usingthe load signals from the load cells.
 11. The system of claim 10,wherein the processing circuitry is further configured to calculate acorrected mass flow rate based on the error.
 12. The system of claim 10,further comprising a data quality sensor configured to generate a dataquality criterion associated with the load cells, the data qualitysensor in electrical communication with the processing circuitry. 13.The system of claim 12, wherein the data quality sensor comprises atleast one sensor selected from the group consisting of a gyroscope, anaccelerometer, a speed sensor, an auger weight sensor, a GPS system, anda header pressure sensor.
 14. The system of claim 12, wherein theprocessing circuitry is further configured to compare the data qualitycriterion to a threshold, and wherein the processing circuitry isfurther configured to disregard the load signal when the data qualitycriterion enters a non-desired range defined by the threshold.
 15. Thesystem of claim 10, wherein each load cell comprises at strain gauge.16. The system of claim 10, wherein the grain tank comprises at leastthree load cells.
 17. A method of calibrating a mass flow sensor of aharvester while harvesting grain, the method including: intercepting aflow of grain with a mass flow sensor; measuring a mass flow rate of thegrain with the mass flow sensor to obtain a measured mass flow rate;storing the grain in a grain tank on the harvester; obtaining loadmeasurements of forces of the grain resting in the grain tank on loadcells at a first time and a second time to obtain a measured change ingrain weight; comparing the measured change in grain weight to themeasured mass flow rate while harvesting grain; determining aninaccuracy in the measured mass flow rate based on the change in grainweight; and correcting subsequent measured mass flow rates based on theinaccuracy.
 18. The method of claim 17, further including: obtaining asignal related to a reliability of the load measurements; and filteringthe load measurements based on the signal.
 19. The method of claim 17,further comprising: determining a rate of change of grain weight, acumulative sum of the mass flow rate, and a rate of change of thecumulative sum of the mass flow rate; and comparing the rate of changeof grain weight to the rate of change of the cumulative sum of the massflow rate.
 20. The method of claim 17, wherein obtaining loadmeasurements of forces of the grain resting in the grain tank on loadcells at a first time and a second time comprises obtaining loadmeasurements of forces on at least three load cells.